The present invention relates generally to the targeting of therapeutic compounds to specific cells. The invention is more particularly related to targeting molecules for use in delivering compounds to non-polarized epithelial cells. Such targeting molecules may be used in a variety of therapeutic procedures.
Improving the delivery of drugs and other agents to target tissues has been the focus of considerable research for many years. Most agents currently administered to a patient parenterally are not targeted, resulting in systemic delivery of the agent to cells and tissues of the body where it is unnecessary, and often undesirable. This may result in adverse drug side effects, and often limits the dose of a drug (e.g., cytotoxic agents and other anti-cancer or anti-viral drugs) that can be administered. By comparison, although oral administration of drugs is generally recognized as a convenient and economical method of administration, oral administration can result in either (a) uptake of the drug through the epithelial barrier, resulting in undesirable systemic distribution, or (b) temporary residence of the drug within the gastrointestinal tract. Accordingly, a major goal has been to develop methods for specifically targeting agents to cells and tissues that may benefit from the treatment, and to avoid the general physiological effects of inappropriate delivery of such agents to other cells and tissues.
In addressing this issue, some investigators have attempted to use chimeric molecules that bind to growth factor receptors on gastrointestinal epithelial cells to facilitate transepithelial transport of therapeutic agents (see WO 93/20834). However, these methods have several disadvantages. For example, such chimeric molecules are transcytosed through the epithelium from the gut lumen and absorbed into the blood stream, resulting in systemic distribution and removal from the epithelium proper. Since the therapeutic agents are targeted specifically away from the epithelium for systemic distribution, these chimeric molecules are generally not useful for treatment of epithelium associated conditions. In addition, TGF-xcex3 or other molecules binding to EGF receptors exhibit many or all of the apparent biological activities of EGF, such as stimulation of enterocyte mitogenesis or suppression of gastric secretion. Such effects collateral to the transcytotic uptake of therapeutic agents may not be desirable or may be contraindicated for intervention of epithelium associated conditions or diseases. Furthermore, EGF receptors are not unique to epithelial cells of the gastrointestinal tract, and can be found on numerous other cells including kidney cells and hepatocytes. Thus, molecules which have affinity for the EGF receptor and are distributed systemically in the blood can be rapidly removed from circulation, accumulated in specific organs and potentially degraded or secreted.
Within an alternative approach, other investigators have employed Fab fragments of an anti-polymeric immunoglobulin receptor IgG to target DNA to epithelial cells in vitro that contain such a receptor (see Ferkol et al., J. Clin. Invest. 92:2394-2400, 1993). Still other researchers have described the translocation of a chimeric IgA construct across a monolayer of epithelial cells in vitro (see Terskikh et al., Mol. Immunol. 31:1313-1319, 1994). Others have used ascites tumor implants in vivo in mice and observed an IgA dimeric antibody produced by subcutaneous tumor cells to accumulate in feces, suggesting that IgA is transported across an epithelial barrier of the gastrointestinal tract (see Greenberg et al., Science 272: 104-107, 1996).
Although epithelial cells are normally aligned with one another to form a protective barrier, preventing bodily entry of toxins and pathogens, aberrations in this cellular alignment are often indicative of disease. In particular, non-polarized epithelial cells present in blood or lymphatic fluid are often indicative of metastatic disease. Eradication of metastatic cells is a fundamental goal of cancer therapy, but conventional techniques such as chemotherapy often result in undesirable side effects.
There remains a need in the art for systems for delivering agents to target epithelial cells, particularly non-polarized epithelial cells which are not aligned with another epithelial cell or cells. The present invention fulfills these needs and further provides other related advantages.
Briefly stated, the present invention provides targeting molecules for the specific delivery of biological agents to epithelial cells. Within certain aspects, the present invention provides a targeting molecule linked to at least one biological agent, wherein the targeting molecule comprises a polypeptide that (a) forms a closed covalent loop; and (b) contains at least three peptide domains having xcex2-sheet character, each of the domains being separated by domains lacking xcex2-sheet character, such that the biological agent is capable of entering and killing a non-polarized epithelial cell. Within specific embodiments, the targeting molecule is linked to at least one biological agent by a substrate for an intracellular or extracellular enzyme associated with or secreted from a non-polarized epithelial cell.
Within another aspect, the present invention provides a pharmaceutical composition comprising a targeting molecule linked to at least one biological agent, as described above, in combination with a pharmaceutically acceptable carrier.
In further aspects, methods are provided for treating a patient afflicted with a disease associated with non-polarized epithelial cells, comprising administering to a patient a pharmaceutical composition as described above. Such diseases include non-small cell lung carcinoma, breast carcinoma, colon carcinoma, ovarian carcinoma, prostate carcinoma, and endometriosis.
Within related aspects, the present invention provides methods for inhibiting the development in a patient of a disease associated with non-polarized epithelial cells, comprising administering to a patient a pharmaceutical composition as described above.
These and other aspects of the present invention will become apparent upon reference to the following detailed description and attached drawings. All references disclosed herein are hereby incorporated by reference in their entirety as if each was incorporated individually.